It is just a guess on my part as I didn't use a starter when I made my mead some five years ago. But that is before I learned the importance of a yeast starter. I would follow the same steps/ quantity of DME that I would for a batch of beer as your yeast starter wort will be a lower OG and shouldn't affect the flavor in the least. You should use yeast energizer in the batch to assist in the fermentation.